Radford’s theory of change shifted from viewing governments as arbitrators between public and private interests on environmental issues, to finding that most governments are captured by industry. Rather than fighting first for new laws, which could be blocked by industries, he has focused on pressuring large companies to change their practices and enlisted them as allies in pushing for strong environmental protections.[10] Examples include Greenpeace campaigns that convinced Apple, Inc. and similar companies to shift to 100% clean energy and lobby utilities and regulators to make that possible,[11][12] as well as work to protect both the Indonesian rainforest and the Bering Sea Canyons.[13][14] Radford argues that the combination of creating industry champions and “outside pressure” focused on the government are the keys to passing new laws to protect the environment.[10] However, Radford has also been a vocal leader calling for the United States to pass campaign finance reform and respect all Americans' voting rights to shift power in politics from corporations towards people and fulfill "the promise of American democracy." Radford is considered by many to be a modern day transcendentalist, in that he is very focused on nature and the environment, and he is an advocate of democracy.[15][16]

Radford began his environmental activism as a high school student at Oak Park and River Forest High School in Oak Park, a Chicago suburb, volunteering for a campaign to stop the building of trash incinerators in the West Side of Chicago near his family's Oak Park home.[17]

From 1999 to 2001 Radford was Field Director for Ozone Action, an organization dedicated to working on the atmospheric threats of global warming and ozone depletion. As field director, Radford planned and executed a number of grassroots campaigns, including a campaign during the 2000 presidential primaries, which was the initial impetus for Senator John McCain sponsoring the Climate Stewardship Act.[20][21]

Radford also managed the grassroots mobilization for the Global Warming Divestiture Campaign, which resulted in Ford, General Motors, Texaco, and other companies ending their funding the Global Climate Coalition, which spread misinformation about global warming.[22] According to the New York Times, the result of the campaign was “the latest sign of divisions within heavy industry over how to respond to global warming.”[23]

As Executive Director of Power Shift, Radford worked closely with the cities of San Diego, Chula Vista, and Berkeley, CA, as well as nine other municipalities, to secure investments for installation of solar energy systems and implementation of energy efficiency measures in municipal buildings.[18] Radford also helped to convince Citigroup to adopt innovative new means of financing clean energy infrastructure for wind and solar installations that made them affordable to average Americans.[4][25]

In 2009, at the age of 33, Radford was selected as the youngest ever Executive Director of Greenpeace.[26][27] Radford’s tenure at Greenpeace USA is best known for convincing over 100 corporations to change their environmental practices;[28] exposing the anti-environmental influence of the Koch Brothers, making them a household name;[29] increasing the organization's net income by 80%;[11] launching the organization’s grassroots organizing and canvass programs;[30] and serving as a founder of the Democracy Initiative,[2] a national coalition of major unions, environmental groups, civil rights and government reform organizations working for universal voter registration, to get money out of politics, and to reform Senate rules. In September 2013, Radford announced that he would step down on April 30, 2014, once he had completed five years of service as Executive Director.[4]

Ben Jealous, former president and chief executive officer of the NAACP as well as co-founder of the Democracy Initiative with Radford, described Radford at the helm of Greenpeace as "a modern movement building giant. He has built powerful diverse coalitions to bolster the fights for the environment and voting rights. In the process he has shown himself to be unmatched in mobilizing everyday people to fund their movements directly.” Environmental leader Bill McKibben stated: “During Radford’s tenure, Greenpeace has been helping the whole environmental movement shift back towards its roots: local, connected, tough.”[11]

Before becoming Executive Director of Greenpeace USA, Radford served as the director of the organization’s Grassroots Program.[26] In that capacity, he started and directed the organization's street and door-to-door canvasses, online-to-offline organizing team, social media team, the Greenpeace Student Network, and the Greenpeace Semester.[33] Under Radford, the street and door-to-door canvassing programs grew to include nearly 400 canvassers in almost 20 cities across the country and was responsible for doubling the organization's budget.[33]

In 2001, while running Power Shift, Radford launched a campaign to push Citibank to offer and promote Energy Efficient Mortgages (EEMs).[37] Citi was "missing the opportunity to help stop global warming by phasing out fossil fuel investments and promoting clean energy now," Radford said. "The irony is that if Citi financed solar for people’s homes, solar energy could be made immediately affordable for millions of Americans today."[38] In 2004, Citigroup agreed to offer and promote EEMs for residential wind, energy efficiency, and solar installations that would make clean energy affordable for millions of Americans.[25]

Radford oversaw the grassroots mobilization efforts on the Kleercut Campaign in the United States and, later, the entire U.S. component of the global campaign when he became Greenpeace’s Executive Director,[26] targeting Kimberly-Clark for sourcing 22% of its paper pulp from Canadian boreal forests containing 200-year-old trees. The campaign included intervening in Kleenex commercial shoots,[39] convincing twenty-two universities and colleges to take action such as cancelling contracts,[40][41] recruiting 500 companies to boycott Kimberly-Clark,[42] over 1,000 protests of the company, and more.[41][43] The result: On August 5, 2009, Kimberly-Clark announced that it would source 40% of its paper fiber from recycled content or other sustainable sources – a 71% increase from 2007 levels. The demand created by Kimberly-Clark for sustainably logged fiber was greater than the supply, enabling the company to convince logging companies to change their practices.[41][44]

From 2010 to 2013, Radford managed Greenpeace US team that persuaded major U.S. companies to cancel their contracts with Asia Pulp and Paper (APP) – the world's third largest paper company[45] – to push APP to stop destroying ancient forests.[46] Greenpeace and its allies succeeded in convincing more than 100 corporate customers of APP to sever their ties with the company,[28] including Mattel,[47]Hasbro,[48]Lego, Kmart,[49]IGA, Kroger, Food Lion, National Geographic, and Xerox.[50] In total, the campaign against APP cut nearly 80% of APP’s U.S. market. On February 5, 2013, Asia Pulp and Paper announced a deforestation policy protecting Indonesian rainforests.[51] Referring to the victory, New York Times reporter Andrew Revkin heralded the campaign with a piece titled: "Activism at Its Best: Greenpeace’s Push to Stop the Pulping of Rainforests".[31]

On April 21, 2011, Greenpeace released a report highlighting data centers, which consumed up to 2% of all global electricity and this amount was projected to increase. Radford stated “we are concerned that this new explosion in electricity use could lock us into old, polluting energy sources instead of the clean energy available today.”[52]Business Insider reported that after Greenpeace USA campaigns, “tech giants like Apple, Google, Facebook, and Salesforce have promised to power their data centers with renewable energy, a pledge that led Duke Energy, the nation's largest power utility and one of the most flagrant emitters of CO2, to begin providing clean energy to win their business.”[12]

In 2014, deforestation in Indonesia, which accounts for .1% of the world’s surface, caused 4% of global warming pollution. One of the major drivers of deforestation was clearing the forest to grow palm oil plantations.[12] Under Radford, the Greenpeace USA team persuaded Procter & Gamble,[12]Colgate Palmolive,[53]Mondelez,[54] and other major companies to demand sustainably grown palm oil.